Aside from the fact that an unloaded gun is at best a poorly balanced club, close to totally useless... compliance with the applicable laws is always a good idea. In most states when traveling in any vehicle the gun must be stored, unloaded in a secure area separate from the ammunition... unless you have a concealed carry permit recognized by that state.
Semi auto's work best as a full magazine that is separate from the pistol can easily and very quickly be inserted and a round chambered in an emergency {though a revolver with a speed loader can accomplish much the same result}.
When in a state, such as California, where my carry permit does not have reciprocity the pistol is kept locked (unloaded) in our digital safe. In an emergency it can be retrieved by my bride in mere seconds and the full magazine resides in my door pocket. The safe also provides secure storage for lots of other things, cash, credit cards, meds etc.. Fort Knox it ain't but it will deter or at least slow down a snatch and grab burglar.
As always.... Opinions and YMMV.
:C